You may have noticed that GIMP is dropped from the Ubuntu 10.04 “Lucid Lynx” installation disc. The reason for getting rid of it as cited by the GIMP developers, is that GIMP is too professional a software to be included in a regular desktop version of Ubuntu. And it takes up too much of space on the disk. Also, the fact that it’s too complicated for regular users.
To install GIMP on Ubuntu 10.04 “Lucid Lynx” you need to add the GIMP 2.7.1 PPA to the software sources of Ubuntu 10.04, to do this open a terminal window (Applications -> Accessories -> Terminal) and copy+paste the following line:
sudo sh -c “echo ‘deb http://ppa.launchpad.net/matthaeus123/mrw-gimp-svn/ubuntu lucid main’ >> /etc/apt/sources.list”
To add the GPG key copy+paste the following line:
sudo apt-key adv –recv-keys –keyserver keyserver.ubuntu.com 405A15CB
To update your software repository copy+paste the following line:
sudo apt-get update
To install GIMP 2.7.1 copy+paste the following line:
sudo apt-get install gimp
When installed you can find GIMP under Applications -> Graphics -> GNU Image Manipulation Program
I found adding ppa instruction simpler.
http://www.khattam.info/howto-install-gimp-2-7-with-single-window-mode-on-ubuntu-lucid-lynx-2010-03-30.html